Oh, don’t get me wrong, I enjoy a working out the metaphysical stuff. I’m kind of a wonk that way. But it’s lower on my list of “to do” when world building than a plausible geography, a sensible history, a logical source of conflict(s), and some verisimilitude of society/culture. Then comes metaphysics.

Obviously, these bits are all interconnected and feed off one another, it’s not like they get built in a vacuum. But it is what I tend to think of doing first, then next, then last. But I do bounce around.

Absolutely. Just because I know how the metaphysics of my settings work doesn't mean the people living in said settings do.

Even better: I don’t have to bother to figure out the metaphysics in the first place!

After reading series like Fullmetal Alchemist and The Dresden Files, I have to admit to preferring to have have all of the rules for how metaphysics work all mapped out beforehand. It creates a nice sense of internal logic that I find most fiction fans appreciate. As one of my friends once put it, "We don't want plausible nearly as much as we want consistent". If you make sure things work the way they're suppose to, not only do you create a bit of verisimilitude, but when those rules get broken, rather than feeling like a "Silver Age-y out the ass power pull", it becomes a plot point that fans can notice and can have some payoff.